A study of polychlorinated dibenzo-p-dioxins and dibenzofurans in the atmosphere of Hong Kong

A total of 27 ambient air samples of were collected from six locations in Hong kong during the period of January-August, 2000 and analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). In all sampling locations, higher concentrations of PCDDs/PCDFs, ranging from 0.03 to 0.43 pg I-TEQ/m3 were measured in winter months (January and March) than in the summer months (July and August) of concentrations at 0.018-0.025 pg I-TEQ/m3. These concentrations are similar to annual ranges reported earlier for two Hong Kong urban sites and other urban cities in Asia. Europe, and the United States. Despite significant seasonal variations in ambient air concentrations of PCDD/Fs (expressed in I-TEQ) were observed, the congener profiles of all the samples in this study period were similar, with OCDD, 1,2,3,4,6,7,8-HpCDD, OCDF and 1,2,3,4,6,7,8-HpCDF being the predominant species. However, the homologue profiles for the samples collected at the six locations of this study were found to display significantly different spatial and seasonal trends.     

Uptake,distribution and immunotoxicological effects of mercury in mice

The uptake and distribution of mercury in various organs and tissues of mice were examined after administration with mercuric chloride (HgCl₂) or mercuric sulphide (HgS). The results show that mice treated with HgCl₂ were found to have significantly higher levels of mercury in various organs and tissues as compared to HgS-treated animals. Except for the kidneys, no significant differences were found in mercury levels between the HgS-treated and control mice. This appears to be due to the higher solubility of HgCl₂, allowing for its greater absorption into the body. Irrespective of the mercurial administered, the kidneys contained the highest concentration of mercury, followed by the liver and brain. Mercury was also found to confer protection against Trypanosoma evansi, possibly due to its toxicity. When treated with HgS, enhanced antibody production and increased levels of circulating leucocytes was seen. HgCl₂ and HgS-treated mice showed no signs of anorexia, no significant changes being found in growth and food intake.     

Biocompatible Polyurethane Scaffolds Prepared from Glycerol Monostearate-Derived Polyester Polyol

Biodegradable polyester polyol was synthesized from oleochemical glycerol monostearate (GMS) and glutaric acid under a non-catalyzed and solvent-free polycondensation method. The chemical structure of GMS-derived polyester polyol (GPP) was elucidated by FTIR, ¹H and ¹³C NMR, and molecular weight of GPP was characterized by GPC. The synthesized GPP with acid value of 3.03 mg KOH/g sample, hydroxyl value of 115.72 mg KOH/g sample and M_n of 1345 g/mol was incorporated with polyethylene glycol (PEG) and polycaprolactone diol (PCL diol) to produce a water-blown porous polyurethane system via one-shot foaming method. The polyurethanes were optimized by evaluating glycerol as a crosslinker, silicone surfactant and water blowing agent on tensile properties of polyurethanes. All polyurethanes underwent structural change, and crystalline hard segments of polyurethanes were shifted to higher temperature suggested that hard segments undergone re-ordering process during enzymatic treatment. In terms of biocompatibility, polyurethane scaffold produced by reacting 100% w/w of GPP with isophorone diisocyanate and additives showed the highest cells viability of 3T3 mouse fibroblast (94%, day 1), and MG63 human osteosarcoma (107%, day 1) and better cell adhesion as compared to reference polyurethane produced by only PEG and PCL diol (3T3 cell viability: 8%; MG63 cell viability: 2%). The current work demonstrated GPP synthesized from renewable and environmental friendly resources produced polyurethanes that allows improvement in physico-chemical, mechanical and biocompatibility properties. By blending with increasing content of GPP, the water-blown porous polyurethane scaffold has shown great potential as biomaterial for soft and hard tissue engineering.     

Thallium in the hydrosphere of south west England

Thallium is a highly toxic metal whose environmental concentrations, distributions and behaviour are not well understood. In the present study we measure the concentrations of Tl in filtered and unfiltered samples of rain, tap, river, estuarine and waste waters collected from south west England. Dissolved Tl was lowest (<20 ng L⁻¹) in tap water, rain water, treated sewage and landfill effluents, estuarine waters, and rivers draining catchments of sandstones and shales. Concentrations up to about 450 ng L⁻¹ were observed in rivers whose catchments are partly mineralized and where metal mining was historically important, and the highest concentration (∼1400 ng L⁻¹) was measured in water abstracted directly from an abandoned mine. Compared with other trace metals measured (e.g. As, Cd, Co, Cr, Cu, Ni, Pb, Zn), Tl has a low affinity for suspended particles and undergoes little removal by conventional (hydroxide precipitation) treatment of mine water.     

氧化还原电位对活性污泥合成聚3-羟基丁酸-co-3-羟基戊酸酯组分的影响

分析了低DO下,乙酸钠、丙酸钠或葡萄糖作碳源,不同氧化还原电位(ORP)对活性污泥合成聚3-羟基丁酸-co-3-羟基戊酸酯(PHBV)的组分和产量的影响.结果显示,ORP从-30mV(厌氧)增加到 100mV(好氧),PHBV共聚物的产量增加,PHBV共聚物中3-羟基戊酸(HV)单体的摩尔分数降低,细胞生长量和碳源利用量增加;乙酸钠作单一碳源,ORP为-30mV时,PHBV共聚物中HV摩尔分数达到21.0%,ORP为 30mV时,PHBV共聚物在细胞内的质量分数达到35.0%.因此,DO是影响活性污泥合成PHBV共聚物的产量以及PHBV共聚物中HV摩尔分数的重要影响因素.     

Degradation pathway of persistent branched fatty acids in natural anaerobic ecosystem

Branched fatty acids (BAFs) in industrial effluents are often persistent in biological wastewater treatment systems and end up as organic contaminants in the water environment. In this study, degradation of eight characteristic BAFs in a natural anaerobic ecosystem of an eutrophic river sediment was studied in vitro by enrichment culture techniques. The anaerobic consortium, comprising of BFA-degrading and methane-producing genera, degraded BFAs with a tertiary carbon through beta-oxidation followed by methanogenesis mechanisms. The consortium could not degrade BFAs with a quaternary carbon. The degree of branching at the alpha or beta position along the carbon chain interfered with the beta-oxidation mechanisms, and hence affected the degradability of the compound.